1. Field of the Invention
The present invention relates to an output paper stacking device of a printing apparatus and, more particularly, to an output paper stacking device of a printing apparatus which has an improved structure for aligning discharged output paper sheets.
2. Description of the Related Art
In general, a printing apparatus 10 such as a printer or copier is provided with a tray 12 as an output paper stacking device for stacking paper sheets discharged through a paper discharge opening 11, as shown in FIG. 1. That is, paper sheets discharged from the printing apparatus 10 by discharge rollers 13 stack on the tray 12 sequentially, and a user must arrange the discharged sheets before taking and using them for their intended purpose after a printing job. Therefore, a pivoting bar 14 as shown in FIG. 1 is used in addition to the output paper stacking device for automatically aligning the sheets since aligning the paper sheets is very troublesome whenever a printing operation is performed. The pivoting bar 14 is driven by a driving unit (not shown) installed in the printing apparatus 10, and is pivoted along an arc track shown in FIG. 1. When the pivoting bar 14 is pivoted as described above, the pivoting bar 14 pushes the paper sheets stacked on the tray 12 toward one side wall 12a of the tray 12. Therefore, since the discharged paper sheets are stacked while they are continually aligned with each other with respect to the one side wall 12a when the pivoting bar 14 is pivoted, there is no need for additionally aligning the paper sheets afterward.
However, when employing the above pivoting bar 14, there are disadvantages in that the number of parts increases, and the structure of the discharge opening 11 side is very complex since a driving unit for driving the pivoting bar 14 must be installed in the printing apparatus 10, and also a sensor for detecting the completion of discharging a paper sheet must be installed. In addition, since the pivoting bar 14 is pivoted whenever a paper sheet is discharged, the consumption of energy for a printing operation increases.
Therefore, an output paper stacking device having a simpler structure adapted to stack discharged paper sheets while aligning the paper sheets is required.
To solve the above problems, it is an objective of the present invention to provide an output paper or printable medium stacking device of a printing apparatus having a simple structure and method which is improved to align the output paper sheets with each other while not requiring an external driving power source, such as an electric motor.
Accordingly, to achieve the above objective, there is provided a printable medium stacking device of a printing apparatus comprising: a tray installed at a position lower than a discharge opening of a printing apparatus so that a printable medium discharged through the discharge opening can stack sequentially. Guide levers are installed so that respective first ends thereof are operative to project upward through respective through slots provided in the tray. The first ends of the guide levers guide both sides of the printable medium discharged from the discharge opening, and align the printable medium at a predetermined position with the respective first ends thereof. Supporting means for rotatably supporting the guide levers are also provided so that the first end of each respective guide lever is balanced by a second end of the guide lever in a state in which the first ends of the guide levers project upward through the through slots of the tray.
The invention also contemplates a method of stacking a printable medium onto a tray after the printable medium is processed by a printing apparatus. The method includes: discharging the printable medium from the printing apparatus and rotatably balancing a first pair of guide levers and at least a second pair of guide levers, the second pair of guide levers having a width that is greater than a width of the first pair of guide levers, and guiding the printable medium between one of the first pair and at least the second pair of guide levers. When the printable medium is guided between the second pair of guide levers, the method further includes depressing the first pair of guide levers into a surface of the tray.